This invention relates generally to drive shafts for automotive vehicles and more particularly to drive shafts that comprise an aluminum torque tube and a connection member at each end of the aluminum torque tube, for connecting the drive shaft in an automotive drive line.
The use of aluminum and aluminum alloy components in place of steel components in automobiles is becoming increasingly popular because a substantial weight reduction can be realized without any sacrifice in strength or durability. Moreover aluminum components are more corrosion resistant than their steel counterparts.
U.S. Pat. No. 4,527,978 granted to Barry L. Zackrisson Jul. 9, 1985 discloses a drive shaft having a heat-treated aluminum alloy torque tube and a heat-treated aluminum alloy yoke or connection member partially telescoped within each end of the tube and joined to it by welding. The torque tube has a constant outside diameter and a wall thickness which is constant throughout most of the length. However, the wall thickness is increased adjacent each end to compensate for reduced hardness resulting from the welding operation.
U.S. patent application Ser. No. 08/692,414 filed Aug. 5, 1996 and assigned to the assignee of this invention, now U.S. Pat. No. 5,672,286 issued Sep. 30, 1997, also discloses a drive shaft having an aluminum torque tube and yokes at each end and a method for welding the aluminum drive shaft components to each other.
The size of the aluminum torque tube used in aluminum drive shafts for automotive drive lines is determined in part by the required length and torque capacity of the drive shaft. An aluminum torque tube having a length in the range of 5 to 6 feet, an outer diameter of 5 inches, and a wall thickness of 0.083 inches is typical. The 5.0 inch outer diameter is larger than a comparable steel drive shaft. However, the end sections of the 5.0 inch outer diameter tube can be reduced in diameter and smaller yokes or other connection members can be used at each end. This reduces space requirements at the drive shaft ends which are usually located in crowded environments. The smaller end sections and yokes also reduce weight significantly particularly when the entire drive shaft assembly is taken into account. The end sections are usually reduced by swaging a larger diameter tube blank.
While such aluminum drive shafts have been found to be generally satisfactory, experience has shown that noise problems are encountered occasionally when thin walled tubes are used. One such noise problem is a periodic tinkling sound initiated by torque reversal when the torque tube has conical transition sections. We have determined that such a sound is due to an instability phenomenon in the conical transition sections which we characterize as oil canning and which we have found is related to the wall thickness of the aluminum tube.
The object of this invention is to provide an aluminum drive shaft comprising a thin walled aluminum torque tube that has reduced diameter end sections that are connected to a larger diameter central section by transition sections that are stable under all normal operating conditions.
A feature of the invention is that the aluminum drive shaft includes a thin walled aluminum torque tube that has reduced diameter end sections that are connected to a larger diameter central section by transition sections that have an annular rib to stiffen the transition sections so as to reduce oil canning and noise.
Another feature of the invention is that the aluminum drive shaft includes a thin walled aluminum torque tube that has reduced diameter end sections that are connected to a larger diameter central section by transition sections that are formed with a concentric cylindrical band located between inner and outer conical portions to stiffen the transition sections so as to reduce oil canning and noise.
Yet another feature of the invention is that the aluminum drive shaft includes a thin walled aluminum torque tube that has reduced diameter end sections that are of sufficient length for use in balancing the aluminum drive shaft.
Still yet another feature of the invention is that the aluminum drive shaft includes an aluminum torque tube that has reduced end sections and transition sections that are formed by swaging the ends of an aluminum tube blank radially inwardly.